This 'Quintessence of Secret (Esoteric) Buddhism' is the combination of the first and second volumes of the previous 'Essence of Secret Buddhism', which were published in the United States in the past two years (1983). It is supplemented with new documents about mystic formulas, Yantras, and Mudras, allowing further studies in Secret Buddhism. Readers are invited to understand and experience the magic and the value of mystic formulas and rituals. The degree of success depends upon the level of one's merits and virtues. Secret Buddhism already has its many wonderful legends in many countries in Asia, so that there is no need to praise it further. It is time for all opinions about the supernatural power and secret doctrine to be presented to humanity like any other science. We invite any skeptical person to try it out before commenting about it.